//
// Sequence.cs
//
// Author:
//   Jonathan Pryor  <jpryor@novell.com>
//
// Copyright (c) 2009 Novell, Inc. (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace zielonka.co.uk.framework.math_ {

	public static partial class Sequence {

		private static readonly Type[] defaultExpandExcept = new[]{
			typeof (string),
		};

		public static IEnumerable Expand (object o)
		{
			return Expand (o, (IEnumerable<Type>) defaultExpandExcept);
		}

		public static IEnumerable Expand (object o, params Type[] except)
		{
			return Expand (o, (IEnumerable<Type>) except);
		}

		public static IEnumerable Expand (object o, IEnumerable<Type> except)
		{
			if (except == null)
				throw new ArgumentNullException ("except");
			return CreateExpandIterator (o, except);
		}

		static IEnumerable CreateExpandIterator (object o, IEnumerable<Type> except)
		{
			IEnumerable e;
			if (except.Any (t => t.IsAssignableFrom (o.GetType ())))
				yield return o;
			else if ((e = o as IEnumerable) != null)
				foreach (var obj in e)
					foreach (object oo in Expand (obj))
						yield return oo;
			else
				yield return o;
		}
	}
}

